Can you check whether the port 1433 is open in the MSSQL server. You need to make sure you can access the port 1433 of your MSSQL server. If it is not open kindly open the port and then check
– vembutechJan 28 '15 at 20:21

SQL Electron

If you don't want to purchase DataGrip, you can use SQL Electron. The steps are similar. Open up SQL Electron, click add to add a new server, and for Server Address type in <server's address>, Port: 1433, and finally your login credentials. And THAT'S IT!